Preparation By Microwave-Assisted And Photocatalytic Activities Of Metal Ion Doped TiO₂/Bentonite Photocatalysts

In this paper,a sodium-type modified bentonite was used as carrier to prepare metal ion doped TiO₂/bentonite photocatalyst by microwave-assisted sol-gel method. Modern techniques such as X-ray powder diffraction(XRD),specific surface area (BET)determination and infra-red spectra(IR)were applied to characterize the photocatalyst,the photocatalytic behavior in degradation reactions of methyl-orange solution and of molasses alcohol wastewater were studied.Several conclusions can be drawn as follows.The optimum conditions of Fe-TiO₂/bentonite photocatalyst prepared by microwave-assisted method were microwave power 750w,tetrabutyl titanate hydrolysis process microwave radiation 5 min,gel drying process microwave radiation 8 min,calcining temperature 550℃,calcining time1.5h.XRD reveals that the size of TiO₂ particles in Fe-TiO₂/bentonite prepared by microwave-assisted method is smaller than those prepared by conventional method. Fe³⁺and Ni²⁺doping can promote phase transformation of TiO₂ from anatase to rutile, but La³⁺doping inhibits this phase transformation of TiO₂,Fe³⁺,Ni²⁺and La³⁺ doping restrain the increase of the grain size of TiO₂.Infra-red spectra(IR)information indicated that titanium bond to the bentonite.BET analysis shows that specific surface area of Fe-TiO₂/bentonite prepared by microwave-assisted method is much larger than that prepared by conventional method.The degradation reaction of methyl-orange solution catalyzed by Fe-TiO₂/bentonite shows that the photocatalytic activity of Fe-TiO₂/bentonite prepared by microwave-assisted method is higher than that of prepared by conventional method,under conditions of Fe-TiO₂/bentonite 2.5g/L,the initial concentration of methyl-orange in solution 20mg/L,the solution pH=4,illumination time 60 min,the degradation rate of methyl-orange is 96.13%.The repeatedly use of the photocatalyst shows that it is catalytically stable during degradation reaction,can be re-used and cause lower costs.The photocatalytic degradation reaction of methyl-orange solution can be expressed as first-order kinetic mode within the concentration range of methyl-orange solution between 20mg/L and 50 mg/L.The degradation reaction of molasses alcohol wastewater catalyzed by Fe-TiO₂/bentonite results that under conditions of dilution 30times,Fe-TiO₂/bentonite catalyst 2.5g/L,original pH,H₂O₂ oxidant consumption 3.0mL/L,illumination time 2h,the degradation rate of molasses alcohol wastewater is 82.94%.